Control circuit for vibratory devices

ABSTRACT

A photoelectric transducer comprising a light emitting diode spaced from the sensitive surface of a phototransistor is mounted on the fixed portion of a vibratory system. A control member on the movable portion of the system is positioned to control the amount of light transmitted from the diode to the phototransistor in accordance with the vibratory amplitude. When the amplitude reaches a predetermined magnitude, as determined by the initial setting of the control member relative to the sensitive surface, the phototransistor is turned on to divert charging current from the timing capacitor in the vibratory motor phase control circuit to limit the vibratory amplitude.

United States Patent Dion [ CONTROL CIRCUIT FOR VIBRATORY DEVICES 5s 1 Field Inventor:

Assignee:

Filed:

Warren E. Dion, Bristol, Conn. Arthur G. Russell Company,

Incorporated, Bristol, Conn.

Jan. 31, 1973 Appl. No.: 328,251

US. Cl 318/128, 318/130, 318/132,

of Search 250/232; 307/211, 252;

. References Cited UNITED STATES PATENTS Evalds et a1 323/21 UX [1 1] 3,840,789 Oct. 8, 1974 3,497,626 2/1970 Guscott et a1. ..323/21X 3,500,455 3/1970 Rossetal ..323/21ux Primary Examiner-D. F. Duggan Attorney, Agent, or Firm-Prutzman, Hayes, Kalb & Chilton [5 7] ABSTRACT A photoelectric transducer comprising a light emitting diode spaced from the sensitive surface of a phototransistor is mounted on the fixed portion of a vibratory system. A control member on the movable portion of the system is positioned to control the amount of light transmitted from the diode to the phototransistor in accordance with the vibratory amplitude. When the amplitude reaches a predetermined magnitude, as determined by the initial setting of the control member relative to the sensitive surface, the phototransistor is turned on to divert charging current from the timing capacitor in the vibratory motor phase control circuit to limit the vibratory amplitude.

7 Claims, 7 Drawing Figures 1 CONTROL CIRCUIT FOR VIBRATORY DEVICES BACKGROUND OF THE INVENTION This invention relates to control circuits for vibratory devices and more particularly to circuits for controlling vibratory feeding equipment such as vibratory bins, hoppers or transport rails.

Vibratory feeders which are operated by electromagnetic vibrators often are provided with phase shift control circuits normally including manual amplitude control or servo amplitude control. The tendency of human operators of such equipment is to turn the manual amplitude control up to the full value, regardless of performance or risk of damage. If the vibratory amplitude could be limited in existing feeder systems, overstressing of vibrator components would be prevented and the flow of conveyed material would be optimized since the optimum condition usually occurs below maximum attainable amplitude.

SUMMARY OF THE INVENTION The principal object of this invention is to provide an improved amplitude control circuit for electromagnetic vibrators which drive vibratory systems.

It is a further object of this invention to provide an improved control circuit which will limit the vibration amplitude of vibrato and the like.

It is 'a further object of this invention toprovide a control circuit for limiting the amplitude of a vibratory device which control circuit is operable at all vibratory amplitudes of the device.

It is a further object of this invention to provide an amplitude limiter for vibratory devices which can be installed easily on existing amplitude controls and in a manner preventing tampering by human operators.

The prevent invention provides a vibratory system controller wherein a photoelectric transducer comprising a light source spaced from a photosensitive surface on the fixed portion of the system cooperates with a y bins, hoppers, transport rails control member on the'movable portion of the system and positioned to control transmission of light to the photosensitivesurface in accordance'with the vibratory amplitude of the system to divert charging current from the timing'capacitor in a phase control circuit controlling the supply of current from an ac. source to the vibratory motor of the system when the vibratory amplitude reaches a predetermined level. The vibratory amplitude is limited or maintained at this level which is determined by the initial setting or rest position, of the control member. The photoelectric transducer comprises a light emitting diode spaced from the sensitive surface of a phototransistor, the collector-emitter path of which is connected in a circuit across the timing capacitor.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is a schematic diagram of an amplitude limiter in a manual vibratory feeder control circuit;

FIG. 2 is a schematic diagram of an amplitude limiter in an automatic vibratory feeder control circuit;

FIG. 3 is a top plan view of an arrangement for mounting an amplitude limiter on a vibratory motor;

FIG. 4 is a sectional view taken about on line 4-4 in FIG. 3;

FIG. 5 is an enlarged sectional view taken about on line 5-5 in FIG. 4; I

FIG. 6 is a fragmentary side elevational view of a vibratory transport rail provided with an amplitude limiter; and

FIG. 7 is a fragmentary end elevational view of the transport rail of FIG. 6.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS In a basic phase-shift control circuit used in vibratory feeder systems, a vibrator solenoid and a controlled rectifier are connected in series across a pair of terminals to which ac. power is supplied. The vibrator solenoid current is controlled to effect a corresponding control of vibratory amplitude by controlling the time at which the controlled rectifier is gated during the positive half-cycle of power line voltage. This can be accomplished by controlling the charging current to a capacitor which is connected by a semiconductor breakdown device such as an avalanche" diode to the control or gate terminal of the rectifier in a manner such that when the voltage across the capacitor equals the critical voltage of the breakdown device, the capacitor discharges through the gate circuit of the rectifier and turns it on. In a manual control scheme a variable resistor is connected in series with the capacitor for controlling the charging current, and in a servo control scheme the charging current is the algebraic sum of several currents, one being proportional to the instantaneous vibratory amplitude, through well-known feedback control principles. A detailed description of phase-shift control circuits for vibratory devices can be found in US. Pat. No. 3,122,690 issued Feb. 25, I964 and assigned to the assignee of this invention.

In accordance with this invention, the vibrator solenoid current is controlled by diverting some of the current normally flowing to the capacitor so that this current is not available for charging the capacitor. The amount of current diverted can be made to increase in correspondence with increasing instantaneous vibratory amplitude of the vibrator, and this diverting or shunting of charging current can be utilized to limit vibratory amplitude. This is accomplished by shunting the capacitor with a resistance means having a magnitude which is varied in accordance with changes in the vibratory amplitude.

In FIG. 1 there is shown a silicon controlled rectifier 1 which rectifier the ac. line voltage applied to terminals 2 and 3 and controls the amount of current supplied to load 4, which load will normally be the winding of the solenoid which drives the vibratory device. A positive gating pulse or signal for controlled rectifier l is generated by discharging timing capacitor 5 through an avalanche diode 6 and current limiting resistors 7 and'8. Any non-linear voltage responsive element possessing operating characteristics similar to diode 6 can be used.

The capacitor 5 is charged toward the critical voltage of diode 6, and when this critical voltage is reached, the diode 6 breaks down thus rapidly discharging capacitor 3 5 and generating a sharp voltage pulse across resistors 7 and 8, which pulse is transferred to the gating terminal of controlled rectifier 1. The charging cycle of capacitor 5 is initiated when the line voltage begins a positive half cycle and the critical voltage for diode 6 is reached sometime during this positive half cycle. By controlling the charging current to capacitor 5 and hence the time required to charge the capacitor to the critical voltage for diode 6, the gating pulse may be produced any time during a positive half cycle of the line voltage, thereby controlling the firing angle of controlled rectifier l and the amount of current delivered to the load.

Current for charging capacitor 5 flows through resistor 9 and variable resistor 10, and the charging current is controlled in part by the values of resistors 9 and 10. The charging current also is controlled by transducer means connected across capacitor 5 and coupled to the element driven by load 4 which transducer means diverts a controlled quantity of charging current from capacitor 5 in accordance with the vibration response of the driven element. In particular, as the vibratory amplitude increases, the amount of charging current diverted from timing capacitor 5 increases whereupon a limiting condition is reached at which no additional charging current can flow into capacitor 5 and at which no further increase in vibratory amplitude can be made.

The transducer is of the photoelectric type including a source of light in the form of a light-emitting diode 11 and a phototransistor 12 having a photosensitive surface or area spaced from diode 11. A control member .13 in the form of a vane or blade of opaque material is operatively connected to the driven element and is positioned between diode l1 and transistor 12 to vary the amount of light incident on the photosensitive surface in proportion to the amplitude of the vibratory motion of the driven element. Diode 11 and transistor 12 preferably are fixed in a juxtaposed position separation by a narrow air gap on the base section of the vibratory motor. Vane 13 preferably is mounted on the movable section of the motor and extends into the air gap so as to interrupt the light path. A preferred mounting arrangement and adjustment mechanism will be shown and described presently.

The light-emitting diode 11 is a two terminal semiconductor device which emits light when forwardbiased. It has the advantages of being a light source which is small in size and requires a relatively low electrical power to provide a usable level of brightness. Typical light emitting diodes require voltage inputs of approximately 1.5 volts and operate at forward currents of approximate 60 milliamperes. Furthermore, it provides a light source which can be switched on and off at high speeds.

The phototransistor 12 is a semiconductor device in which holes are generated by light absorption and produce a multiplied photocurrent by transistor action at the collector. The phototransistor has the characteristic of allowing more current to flow in the collectoremitter circuit thereof as the amount of light incident on the sensitive area or surface of the transistor increases, i.e. conducting more current when illuminated than when dark. Of course any current conducting photosensitive element possessing similar operating characteristics may be used, such as a photosensitive resistor.

The collector-emitter path of phototransistor l2 and a current limiting resistor 14 are connected across timing capacitor 5 so as to provide a controlled shunt path for current which otherwise would flow into capacitor 5. Diode 11 is connected to a direct current source comprising rectifier l5 and current limiting resistor 16, the series combination of diode 11, rectifier l5 and resistor 16 being connected across terminals 2 and 3. Diode 1] and rectifier 15 are poled so as to operate only on the positive half-cycle of the line voltage on the terminals 2 and 3 so as to obviate the need for a filtered dc. power supply for diode 11.

Other components of the circuit of FIG. I perform the following functions. Diode 17 is provided to prevent build-up of reverse voltage across avalanche diode 6 during the negative half of the line voltage cycle. A varistor 18 is provided to prevent the generation of inductive spike voltages which could damage controlled rectifier 1 when the load current is shut off. Resistor l9 augments the holding current supply to the SCR. A fuse 20 limits damage caused by a circuit fault, and a switch 21 controls application of line voltage to the load 4.

The operation of the controller of FIG. 1 is as follows. Vane 13 is initially disposed so as to interruptor block the light beam from diode 11 so that substantially no light is incident on the photosensitive surface of phototransistor 12 and substantially no current flows in the collector-emitter circuit of phototransistor 12. When current is supplied to load 4 to operate the vibratory motor, vane 13 reciprocates or vibrates in the space or gap between diode 11 and the sensitive surface of phototransistor 12 at the same amplitude and frequency as the vibrating member to which it is connected. The frequency is determined by the line voltage frequency, normally hertz. As the amplitude of vibration is increased the distance through which vane 13 is moved or displaced from its initial position during each cycle of the vibratory movement increases and the amount of light incident on the photosensitive surface increases. Phototransistor 12 is turned on and the flow of current through the collector-emitter path increases and reaches saturation when the light beam to the photosensitive surface is completely restored.

When the vibratory amplitude is at zero or relatively low levels, substantially no light is incident on the photoelectric receiver 12, and the combination of resistor 14 and phototransistor 12 has a negligible effect on the control circuit. The circuit is operated as a manual controller with the charging rate of timing capacitor 5 being controlled by the manual setting of variable resistor 10. When the voltage across capacitor 5 reaches the critical point, diode 6 breaks down thus producing a positive voltage spike which is applied to the gating terminal of the silicon-controlled rectifier 1. This voltage pulse fires the controlled rectifier 1, thus providing load current to the load 4.

If the setting of variable resistor 10 is manually varied to increase the charging rate of capacitor 5, controlled rectifier 1 is fired earlier in the positive half cycle of the line voltage to provide a larger current to load 4. The vibratory amplitude increases, and when the vibrating element and vane 13 move far enough during each excursion to expose the sensitive surface of phototransistor 12 to the light beam from diode 11, current is diverted away from charging the capacitor 5 and flows instead through resistor 14 and the collector-emitter path of phototransistor 12. As a result, controlled rectifier 1 is fired later in the cycle and vibrator solenoid current is reduced to cause a corresponding reduction in vibratory amplitude. lf resistor is varied further in magnitude in an attempt to increase vibratory amplitude, vane 13 is vibrated at a greater amplitude thereby exposing more of the photosensitive surface to the light beam and increasing the conduction of transistor 12. A limiting condition on vibratory amplitude develops at the point where the light beam is completely restored to the photosensitive surfaceor area. Phototransistor 12 then is in saturation and any additional current flowing toward timing capacitor 5 is diverted or shunted through resistor 14 and the collector-emitter path of transistor 12. This prevents firing controlled rectifier 1 any earlier in the positive half-cycle of the line voltage and prevents any further increase in vibratory amplitude. A mechanical load applied to the vibratory system tends to reduce its vibratory amplitude, thus reducing the vibratory amplitude of vane 13. If this happens to reduce the amount of light incident on phototransistor 12, the setting of variable resistor 10 can be advanced to increase the vibratory amplitude up to the limit established by the combination of diode l1, phototransistor l2 and vane 13. By adjusting the initial or rest position of vane 13 relative to the photosensitive surface, the distance through which vane 13 must move or travel during each cycle of vibratory movement to completely expose the photosensitive surface is adjusted. This in turn provides adjustment or control of the level or value at which vibratory amplitude is limited.

The arrangement of FIG. 1 provides a maximum vibratory limit control such that adjustment of the manual control, i.e. the setting of variable resistor 10, is effective only up to the maximum limit as determined by the combination of diode 11, phototransistor l2 and vane 13. This not only prevents overdriving of the vibratory device but also sharply defines optimum vibratory conditions when the setting of resistor 10 is advanced to the position of permitting the transducer combination to control. During machinery setup conditions, it is sometimes desirable to operate the vibratory system at an amplitude less than the optimum amplitude to facilitate adjustment of related parts and machinery.

The arrangement of FIG. 1 illustrates the ease and economy with which an existing manual controller can be provided with an automatic amplitude limit control. A relatively small amount of additional circuitry is required in the form of diode ll, rectifier l5 and resistor 16 connected across terminals 2 and 3 together with phototransistor l2 and resistor 14 connected across timing capacitor 5. Furthermore, the transducer combination of diode 11 and phototransistor l2 and the control member or vane 13 is installed easily in existing vibratory systems as will be apparent presently.

Where it is desired to limit vibratory amplitude in an automatic load compensation circuit, some of the above principles can be utilized in an automatic controller circuit as shown in FIG. 2. When the control is first switched on, control member or vane 25 is in the initial or rest position blocking or interrupting the light beam provided by light emitting diode 26 so that initially no light is incident on the photosensitive surface or area of phototransistor 27 so that substantially no current flows in the collector-emitter circuit of transistor 27. When the line voltage applied across terminals 28 and 29 goes positive, current flows through either potentiometer 30 or switch 31 if closed and through resistors 32 and 33 to cause an intermediate charging of timing capacitor 34. Avalanche diode 35 breaks down to cause an early firing of controlled rectifier 36 with consequent large load current being applied to the load- 37. As the vibratory amplitude increases, the excursions or deflections of vane 25 increase allowing more light to be transmitted to the sensitive area of phototransistor 27. The increase conduction of phototransis tor 27 diverts more charging current away from timing capacitor 34 thereby firing controlled rectifier 36 later in the positive half cycle to reduce the supply of current to load 37 and reduce the vibratory amplitude. When the light beam to phototransistor 27 is completely restored, any additional current flowing toward capacitor 34 flows instead through the collector-emitter path of transistor 27 and further increase in vibratory amplitude is prevented. A mechanical load applied to the vibratory system tends to reduce its vibratory amplitude, thus reducing the vibratory amplitude of vane 25. If this reduces the amount of light incident on the photosensitive surface or area of phototransistor 27, the effect of transistor 27 on the circuit likewise is reduced and more charging current is allowed to flow to timing capacitor 34 causing controlled rectifier 36 to feed more current to load 37 tending to maintain a constant vibratory amplitude at the limit established by the combination of vane 25, diode 26 and phototransistor 27. By adjusting the initial position of the control member or vane 25 with respect to the photosensitive surface or area of phototransistor 27, the point at which vibratory amplitude is limited is predetermined.

When potentiometer 30 is connected in the circuit it enables the flow of current to timing capacitor 34 to be varied so as to allow the operator to reduce the vibratory amplitude below the level established by the combination of vane 25, diode 26 and phototransistor 27. It of course cannot increase the vibratory amplitude above that established level. When potentiometer 30 is not needed switch 31 is closed. Diode 26 is connected to a direct current source comprising rectifier 38 and current limiting resistor 39, the series combination of diode 26, rectifier 38 and resistor 39 being connected across terminals 28 and 29. Diode 26 and rectifier 38 are poled so as to operate only on the positive halfcycle of the line voltage on the terminals 28 and 29 so that a filtered dc. power supply for diode 26 is not needed. Diode 40, varistor 41, resistor 42 and fuse 43 perform functions identical to those performed by diode 6, varistor '18, resistor 19 and fuse 20, respectively, in the circuit of FIG. 1. Avalanche diode 35 is connected through current limiting resistors 44 and 45 to the control or gate terminal of controlled rectifier 36.

The controller of FIG. 2 has the same advantage as the controller of FIG. 1 in providing a vibratory amplitude limiter which is readily and easily incorporated into an existing controller with a relatively small amount of additional circuitry and by a convenient and easy mounting or installation procedure. Both controllers have the additional advantage of being able to limit vibratory amplitude at any selected level, in other words there is no minimum amplitude below which the limiter will not work. The level or value of vibratory amplitude at which the limiting condition occurs is dependent solely upon the adjusted initial or rest position of the control member or vane relative to the photosensitive surface. Theoretically it is possible to limit at zero amplitude-by setting the initial position of the vane to completely expose the sensitive surface to the light beam. Limiting could be made to occur at a minute amplitude, only very slightly greater than zero, by having the initial position of the vane expose all but a very small portion of the photosensitive surface. Normally, the adjusted initial or rest position of the vane relative to the photosensitive surface will completely block or shade the surface from the light beam.

The combination of a light emitting diode and phototransistor, both of which switch electrical states or conditions at high speed, contributes to a system having a time constant which is substantially zero thereby practically eliminating overshoot and resulting in good dynamic stability.

The control member or vane is of opaque material such as metal, but it may be possible to use a semiopaque material or perhaps even a translucent material if the phototransistor or equivalent device can exhibit the desired electrical output characteristic when the material is placed between the photosensitive area of the device and the light source.

FIGS. 3-5 show a preferred arrangement for mounting the transducer and vane on a vibratory motor 50 used for driving vibratory feeding equipment such as vibratory bowls, hoppers, bins, transport rails and conveyors. Motor 50 is a self-contained magnetic motor such as the Vibro Block motor sold by Arthur G. Russell Co., Inc. Motor 50 has a fixed section or face 51 and a movable section or face 52 which vibrates during operation of the motor in the direction indicated by arrows 53 in FIG. 4.

The transducer comprising the light emitting diode and phototransistor is available as a unit 54 from the General Electric Company and identified as Photon Coupled lnterrupter Module H l 381. The photoelectric unit 54 comprises a light transmitting portion 55 containing the light emitting diode and a light receiving portion 56 containing the phototransistor, the two portions being separated by an 'air gap. Unit 54 is fastened to one surface of a positioning member 57, the opposite surface of which slidably contacts a surface of a housing 58 which is fastened to a bracket 59 mounted on the fixed face 51 of motor 50. Positioning member 57 has a flange or extension 60 which projects into a cavity of housing 58 and which flange 60 is operatively connected to an adjusting means comprising biasing springs 61 positioned between a surface of flange 60 and an inner surface of housing 58 and an adjusting screw 62 mounted for rotation in housing 58 and threadably received in flange 60. Unit 54 is moved either up or down as viewed in FIG. 4, depending upon the direction which screw 62 is turned, to a position which is maintained or held by springs 61. An electrical cord 63 fits through an opening in housing 58 to connect unit 54 to the controller circuit.

A control member or vane 64 is fastened at one, end thereof to the movable face 52 of motor 50 and is positioned or disposed so as to extend into the air gap of unit 54 so as to interrupt or block light traveling from transmitting portion 55 to the photosensitive surface or area 65 of receiving portion 56. Vane 64 is provided with a slot 66 at the free end whereby each edge of the slot 66 serves as a separate vane or control member, both being provided on a single member for convenience of manufacture and application. In use, one

edge or the other of slot 66 is active, depending upon the side of motor 50 upon which the transducer unit 54 is mounted. The direction of motion of the active edge of vane 64 with respect to light sensitive area must be from a position blocking the light beam to a position allowing light to be incident on surface 65, i.e. from dark to light. The opposite would result in a condition of regenerative feedback, causing the system to jump to full amplitude. The need for left-hand or right-hand mounting of the vane or control member, due to the opposite directions of vibratory motion in reference to opposite sides of motor 50, is satisfied by the two edges of slot 66 in vane 64.

Unit 54 is relatively small, being about one inch in length, thereby affording convenient installation on motor 50. A mask 67 can be fitted on unit 54 to limit the amount of background illumination entering the air gap.

Assuming that during each cycle of operation of motor 50 face 52 moves in a downward direction on the power pulse and then returns in an upward direction as viewed in FIG. 4, the lower edge of slot 66 is the active edge of vane 64 for this mode of operation. For purposes of illustration, vane 64 is in a position exposing photosensitive surface 65 to view in FIG. 4. Screw 62 is turned to move positioning member 57 and unit 54 in a downward direction so that the active portion of vane 64 blocks transmission of light to surface 65. The greater the amount by which unit 54 is adjusted in a downward direction relative to the edge of vane 64, the higher will be the level of vibratory amplitude required to completely expose surface 65 and limit or prevent any further increase in vibratory amplitude. It is apparent that the width of slot 66 must be equal to or greater than the dimension of photosensitive surface 65 measured along the direction of vibratory motion when complete exposure of surface 65 is to cause amplitude limiting.

The arrangement of FIGS. 3-5, wherein unit 54 and vane 64 are mounted on motor 50, provides a tamperresistant vibratory amplitude limiter control for vibratory feeding equipment. This is because the vibratory motor is normally inaccessible to operators of such equipment, the motor being located within the base of vibratory bowls for example. The controller circuit is contained in a suitable box or housing whereby manually-operable components such as switches and potentiometers are accessible to the operator. Furthermore, theforegoing arrangement is economical and longlasting and can be installed relatively quickly and easily by the user of existing equipment.

FIGS. 6 and 7 illustrate a typical arrangement for mounting the transducer and vane on a vibratory transport rail or conveyor. A relatively heavy base or mass bar is supported on the floor or ground by shock mounting springs not shown) and comprises the relatively stationary portion of the vibratory system. A vibratory motor 76, which can be identical to motor 50 of FIGS. 35 is fastened at the fixed end or base thereof to a bracket 77 mounted on mass bar 75. The movable face of motor 76 is fastened to a depending flange portion of a parts transfer rail 78 which comprises the moving portion of the vibratory system. The direction of vibratory motion is indicated by the arrows in FIG. 6. Two or more vibratory motors usually are required; however, relatively short rails can be carried upon a single vibrator. A photoelectric transducer unit 79 identical to unit 54 in FIGS. 3-5 is adjustably connected to a bracket 80 mounted on mass bar 75. A control member in the form of a single blade or vane 81 is fixed to rail 78 and positioned to extend into the air gap of transducer unit 79 to control the amount of light incident on photosensitive surface or area 82 in accordance with the amplitude of the vibratory motion.

From the foregoing description of the structure and operation of the illustrated embodiments of this invention, it is apparent that an improved vibratory system control circuit has been provided to supply half-wave current from an ac. power line to the drive mechanism of a vibratory device and to limit the current and hence the vibratory amplitude at a selected value.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above described will become readily apparent without departure from the'spirit and scope of the invention, the scope of which is defined in the appended claims.

I claim:

1. In a vibratory system having a fixed portion and a movable portion driven by a vibratory motor, a controller for supplying current from an ac. source to said motor, said controller comprising:

a. photoelectric transducer means on said fixed portion, said transducer means comprising a light source and a photosensitive surface spaced from said light source, said transducer having an electrical output quantity which changes according to the amount of light incident on said surface;

. a control member on said movable portion and positioned in the space between said light source and said photosensitive surface to control the amount of light incident on said surface in accordance with I the amplitude of the vibratory motion generated by said motor; and

c. circuit means connected to the output of said transducer means and to said source and to said motor to control the amount of current supplied to said motor as determined by the output of said transducer means, said circuit means comprising a controlled rectifier connected between said a.c. source and said motor and a timing capacitor coupled in controlling relation to said controlled rectifier and said transducer means comprising means to provide a shunt path for charging current across said capacitor when said control member exposes said photosensitive surface to a predetermined amount of light whereby the amplitude of vibratory motion is limited.

2. The vibratory system controller recited in claim 1 and means to adjust the initial relative position between said control member and said photosensitive surface to adjust the value at which the amplitude of vibratory motion is limited.

3. The vibratory system controller recited in claim 1 v wherein said photoelectric transducer means comprises a light emitting diode, means to apply a forward bias voltage across said diode, a phototransistor having a photosensitive surface spaced from said diode, and

means to connect the collector-emitter path of said 5 phototransistor across said timing capacitor.

4. A vibratory device controller for supplying current from an ac. source to a load which drives a controlled element in a vibration mode, said controller comprismg:

a. a controlled rectifier having two power terminals and a gating terminal, said two power terminals being connected in series with said a.c. source and said load;

b. a timing capacitor;

c. means to supply charging current to said timing capacitor from said a.c. source;

(1. voltage responsive means connected to said timing capacitor and to said gating terminal and operative when the voltage across said timing capacitor reaches a critical point to produce a gating signal which fires said controlled rectifier; and

e. current controlling means connected across said timing capacitor and operatively coupled to the driven element to divert charging current from said timing capacitor in accordance with the vibration response of the driven element, said current controlling means comprising photoelectric transducer means fixed relative to'said driven element and comprising a light source and a photosensitive surface spaced from said light source, said current controlling means further comprising a control member on said driven element and located in the space between said light source and said photosensitive surface to control the amount of light incident on said surface in accordance with the vibratory amplitude of said driven element, said current controlling means providing a shunt path for current across said timing capacitor when a predetermined amount of light is incident on said photosensitive surface at a predetermined value of the vibratory amplitude to prevent any increase in vibratory amplitude in excess of said predetermined value.

5. The vibratory device controller recited in claim 4 and means to adjust the initial position of said photosensitive surface relative to said control member to adjust said predetermined value of vibratory amplitude.

6. The vibratory device controller recited in claim 4 wherein said means to supply charging current to said timing capacitor comprises variable resistance means to vary the vibratory amplitude in the range below said predetermined value.

7. The vibratorydevice controller recited in claim 4 wherein said photoelectric transducer means comprises a light emitting diode, means to supply forward bias voltage across said diode, a phototransistor, and means to connect the collector-emitter path of said transistor across said timing capacitor. 

1. In a vibratory system having a fixed portion and a movable portion driven by a vibratory motor, a controller for supplying current from an a.c. source to said motor, said controller comprising: a. photoelectric transducer means on said fixed portion, said transducer means comprising a light source and a photosensitive surface spaced from said light source, said transducer having an electrical output quantity which changes according to the amount of light incident on said surface; b. a control member on said movable portion and positioned in the space between said light source and said photosensitive surface to control the amount of light incident on said surface in accordance with the amplitude of the vibratory motion generated by said motor; and c. circuit means connected to the output of said transducer means and to said source and to said motor to control the amount of current supplied to said motor as determined by the output of said transducer means, said circuit means comprising a controlled rectifier connected between said a.c. source and said motor and a timing capacitor coupled in controlling relation to said controlled rectifier and said transducer means comprising means to provide a shunt path for charging current across said capacitor when said control member exposes said photosensitive surface to a predetermined amount of light whereby the amplitude of vibratory motion is limited.
 2. The vibratory system controller recited in claim 1 and means to adjust the initial relative position between said control member and said photosensitive surface to adjust the value at which the amplitude of vibratory motion is limited.
 3. The vibratory system controller recited in claim 1 wherein said photoelectric transducer means comprises a light emitting diode, means to apply a forward bias voltage across said diode, a phototransistor having a photosensitive surface spaced From said diode, and means to connect the collector-emitter path of said phototransistor across said timing capacitor.
 4. A vibratory device controller for supplying current from an a.c. source to a load which drives a controlled element in a vibration mode, said controller comprising: a. a controlled rectifier having two power terminals and a gating terminal, said two power terminals being connected in series with said a.c. source and said load; b. a timing capacitor; c. means to supply charging current to said timing capacitor from said a.c. source; d. voltage responsive means connected to said timing capacitor and to said gating terminal and operative when the voltage across said timing capacitor reaches a critical point to produce a gating signal which fires said controlled rectifier; and e. current controlling means connected across said timing capacitor and operatively coupled to the driven element to divert charging current from said timing capacitor in accordance with the vibration response of the driven element, said current controlling means comprising photoelectric transducer means fixed relative to said driven element and comprising a light source and a photosensitive surface spaced from said light source, said current controlling means further comprising a control member on said driven element and located in the space between said light source and said photosensitive surface to control the amount of light incident on said surface in accordance with the vibratory amplitude of said driven element, said current controlling means providing a shunt path for current across said timing capacitor when a predetermined amount of light is incident on said photosensitive surface at a predetermined value of the vibratory amplitude to prevent any increase in vibratory amplitude in excess of said predetermined value.
 5. The vibratory device controller recited in claim 4 and means to adjust the initial position of said photosensitive surface relative to said control member to adjust said predetermined value of vibratory amplitude.
 6. The vibratory device controller recited in claim 4 wherein said means to supply charging current to said timing capacitor comprises variable resistance means to vary the vibratory amplitude in the range below said predetermined value.
 7. The vibratory device controller recited in claim 4 wherein said photoelectric transducer means comprises a light emitting diode, means to supply forward bias voltage across said diode, a phototransistor, and means to connect the collector-emitter path of said transistor across said timing capacitor. 